How can I turn the frames rendered by blender in an animation into a video?
Open Blender and go to the video sequence editor view.
Add->Image. Select to the folder with all you images and select them with a (all), b (box select), or shift+click (single select). Press "Add Image Strip"
You image sequence will be added as strip
Set start and end frame according to the strip's size.
Go back to the default view.
In the rendering tab of the Properties panel, make sure that "Sequencer" is checked in "Post Processing".
In "Output", set the wished video format, compression and out file
Render the animation (Ctrl+F12)